/Engine/Source/Runtime/AudioMixer/Public/AudioMixerDevice.h
Builds a channel gain matrix for a non-spatialized source. The non-static variation of this function queries AudioMixerDevice->NumOutputChannels directly which may not be thread safe.
static void Get2DChannelMap ( bool bIsVorbis, const int32 NumSourceChannels, const int32 NumOutputChannels, const bool bIsCenterChannelOnly, [Audio::FAlignedFloatBuffer](API\Runtime\SignalProcessing\DSP\FAlignedFloatBuffer) & OutChannelMap )